Art of separating mixed gases



March 13, 1934. w. L. DE BAUFRE 1,951,135

ART OF SEPARATINGMIXED GASES Filed. June 16, 1931 2 Sheets-Sheet 1 NVENTOR ATTORN EY' arch 1'3, 1934-. w DE B U E 1,951,15

' ART OF SEPARATINGMIXED GASES Filed June 16, 1931 2 Sheets-Sheet 2 INVENTOR I ATTORNEY! Patented Mar. 13, 1934 ,umrao STATES PATENT OFFICE 1,951,185 ART or SEPARATING MIXED GASES William L. De Baufre, Orange, N. J. Applicationfiune J16, 1931, Serial No. 544,735 13 Claims. (01. 62-122) This invention relates to improvements in the art of separating mixed gases, the invention being particularly useful in separating air and obtaining very high purity oxygen or nitrogen or both.

One of the primary objects of the invention is to simply and effectively remove impurities and more particularly lubricants carried into the systern from thecompressors.

Another object of the invention is to recover more highly volatile gases in a relatively pure state.

More specifically the invention has to do with the provision of a novel and improved arrangeinent of vaporizer portions of rectifying columns for providing the liquid refiuxes in the system.

The foregoing, together with such other objects and advantages as may hereinafter appear, or are incident to the invention, are realized by the construction which Ihave illustrated in the pre-- ferred form in the accompanying drawings, wherein Fig. 1 is a diagrammatic view partially in side elevation and partially in section illustrating-one form of the invention, and I Fig. 2 is a similar view illustrating another form of the invention.

Referring now to the drawings the air separation plant comprises two intrchangers A and B, a liquefier C, an exchanger K, a purifier M- and a rectifying column made up ofa pot E, a preliminary tray section F, a vaporizer section G, and a main tray section H. An expansion engine D may be provided as shown in Fig. 1 or the necessary refrigeration can be obtained by throttling as indicated in Fig. 2.

Air compressed to the necessary operating pressure enters the system at the air inlet 1. With valves 2, 5 and '7 open and valves 3, 4 and 6 closed, the compressed air passes through interchanger A and then through interchanger B, leavingthe' latter through pipe 8. Valves 9 and 10 should be closed and valves 12 and 13 open. Then the nitrogen from the rectifying column and the oxygen from the exchanger will be returning through interchanger B and not through interchanger A. In interchanger B, the compressed air will be cooled by the returning oxygen and nitrogen.

After leaving-interchanger B, the compressed air may all pass into liquefier C as indicated in Fig. 2, or it may divide as indicated in Fig. 1, part going to expansion engine D through pipe 16. Liquefaction is produced in liquefier C by the returning oxygen from exchanger K and the returning nitrogen from the maintray section H.

The preliminary tray section F contains a number of trays arranged to cause the rising vapor to bubble through liquid flowing down from tray to tray. In Fig. 1, the expanded air from expansion engine D is introduced near the bottom of the preliminary tray section while the liquefied air from liquefier C is introduced into a tray some distance above the bottom. In Fig. 2,.the partly liquefied air from liquefier C first passes through the coil in potE before being throttled through valve 62 into one of the trays of the preliminary e5 tray section.

Leaving the uppermost tray of the preliminary tray section, the vapor of nearly pure nitrogen passes through pipe 23 external to the column to the space above the upper tube sheet of vaporizer 71,; section G. The vapor then passes down through a larger number of small tubes25 in the vaporizer section and is partly condensed. Selective liquefaction is avoided in the vaporizer section by having the vapor partially liquefy as it passes downward through the tubes therein. The remaining vapor leaves through pipe 26. The liquefied portion passes through liquid sealed tubes 27 and forms the reflux liquid for the preliminary tray section. 1

This reflux liquid interacting with the rising vapor tmough the trays of the preliminary tray section causes an oxygen-rich liquid to collect in pot E. This liquid is throttled through pipe 30 by means of valve 31 and enters the main tray 85 section at 32. Flowing-down from tray to tray, this liquid finally flows through pipe 33 to the space surrounding the tubes in vaporizer section G. The liquid will boil by heat transfer from the condensing vapor within the tubes and the resulting vapor will leave through pipe 34 and enter the bottom of the main tray section.

In the vaporizer mection G the oxygen-rich liquid isfractionated-by boiling so that the portion 1 of this liquid leaving; through pipe 36 is of higher purity than the liquid entering the vaporizer section. In exchanger K, the vaporization of the oxygen-rich liquid is completed, part of the resulting vapor returning through pipe 39 to lique fier C while the remainder returns through pipe 41 to the main tray section of the rectifier.

The constant flow of liquid from vaporizer section Ginto exchanger K carries with it lubricant which has passed into the system from the com pressor and this lubricant will accumulate in the exchanger K. By closing valve 36 the liquid in exchanger K will partially boil away and the remaining liquid may be discharged through a. drain 52 provided for that purpose, thus carrying out of the system completely all the accumulated lubricant. The operation of the rectifying column will be-affected but slightly by so doing and normal operation is quickly attained by reopening valve 36. Thus the accumulation of lubricant is completely discharged from the system with very little loss of liquid oxygen.

The vapor which left vaporizer section G through pipe 26 enters exchanger K and passes I upward through the tubes therein where its liquefaction is completed, with the exception of a small portion containing the more volatile gases neon, hydrogen and helium. An upward flow is used in'this exchanger in order, by selective liquefaction, to obtain these more. volatile gases at the into the top of the main tray section H of the rectifier in which it serves as a reflux liquid.

The gaseous mixture from exchanger K which enters the coil within purifier M is there brought into heat exchange relationwith liquid nitrogen, aiter being'throttled through valve 44. It

had previously been in heat exchange relation with liquid o ygen which vaporizes at an appreciably higher temperature under the. same pressure as liquid nitrogen. The more volatile gases are, therefore, further purified of nitrogen which is liquefied and separated in pot 48, returning to pct 43 through pipe 49. The purified rare gases are recovered through pipe containing valve 51. In large plants the refrigeration corresponding to the low temperature of these volatile gases may be utilized by returning them throughthe liquefier and interchangers.

The external exchanger K is mounted at substantially the same level as the vaporizer section G of the rectifier. As the level of the liquid oxygen within the exchanger K and vaporizer G will be approximately the same, the tubes therein will be equally submerged in liquid whatever this level may be. For a system to produce high purity oxygen the refluxes in the preliminary and main rectiflers should be approximately the same. This requires equal amounts of heating surface in the exchanger K and the vaporizer section G. These are, therefore, made of approximately the same number of tubes.

In general the plan of operation is in accordance with the disclosure in my copending application Serial No. 544,734, filed June 16, 1931, v V

Y tion, a main tray section and a vaporizer interexe'cuted of even date.

I claim:-= ,7

.1. In a system for separating gas'es, av

rectifying column having a preliminary tray sec-. tion, a main tray section and a vaporizer intermediate the same, and external heat exchanger mechanism for completing the vaporization of the liquid from the main tray section and sub-"- stantially completing the liquefaction of the vapors from the preliminary tray section.

2. In a system for separating mixed gases, a rectifying column having a preliminary tray section, a main traysection and a vaporizer intermediate the same for providing reflux liquid for the preliminary tray section, and external heat exchanger mechanism providing the reflux liquid forthe main tray section by liquefying the vapor of the preliminary traysection not liquefied in the vaporizer.

system for mixedj gases, '9.

rectifying column having means for collecting the liquidcomponent, and means for vaporizing said component, said last means comprising two vaporizer compartments connected in series, one of which partially vaporizes the liquid and the other-of which completes said vaporization, and means whereby the latter compartment may be shut off from the former compartment and drained of liquid. r

4. In a system for separating mixed gases, a rectifying column having a preliminary tray section, a main tray section and a vaporizer intermediate the same, external heat exchanger mechanism forcompleting the vaporization of the liquid from the main tray section and substantially completing the liquefaction of the vapors from the preliminary tray section, and means for withdrawing the vaporized liquid component from the external exchanger.

5. In asystem for separating mixed gases, a rectifying column having a preliminary tray section, a main tray section and a vaporizer intermediate the same, and external heat exchanger mechanism for completing the vaporization of the liquid from the main tray section and substantially completing the liquefaction of the vaporsfrom the preliminary tray section, the external exchanger beingat substantially the same level as the vaporizer so that the tubes of each are substantially equally submerged in liquid.

6. In a system for separating mixed gases, a

rectifying column having a preliminary tray section, a main tray section and a vaporizer intermediate the same, and external heat exchanger mechanism for completing the. vaporization .of

the liquid from the main tray section and substantially completing the liquefaction of the vapors from the preliminary tray section, the exter'nal exchanger being at substantially the same level as the vaporizer so that the tubes of each are substantially equally submerged in liquid and the surfaces of the exchanger and vaporizer being substantially equal.

'7. In a system for separating mixed gases, a

rectifying column having a preliminary tray section, a main tray section and a vaporizer intermediate the same comprising a plurality of verticaitubes connected to tube sheets, a connec tion for leading vapor from the preliminary tray section to the upper ends of said tubes,' and a connectionfor leading liquid from the vaporizer to the preliminary tray section.

8. In a system for separating mixed gases, a.

rectifying column having a preliminary tray'secconnection for"leading liquid from thevaporizer v v to the preliminary tray section.

9. In a system for separating mixed gases, 9. rectifying column having a preliminary tray section, a main tray section and a vaporizer intermediate the same comprising a plurality of vertical tubes connected to tube sheets, and'a connection for leading vapor from the preliminary tray section to the upper ends of said tubes.

'a' connection for discharging non-condensed vapor from the vaporizer and alliquid seal, for V, V

returningliquid from the vaporizer to the preliminary tray section.

10. In a system for separating mixed gases.

a rectifying column-having a preliminary tray section, a main tray section and a vaporizer intermediate the same. and external heat exchanger mechanism for completing the vaporization of the liquid from the main tray section and substantially completing the liquefaction of the vapors from the preliminary tray section, the flow in the tubes of the external exchanger being upward, and means for discharging uncondensed vapor from the top of the exchanger. 11. In a system for separating mixed gases. a rectifying columnhaving a preliminary tray section, a main tray section and a vaporizer intermediate the same, and'external heat exchanger mechanism for completing the vaporization of the liquid from the main tray section and substantially completing the liquefaction of the vapors fromthe preliminary tray section, the flow in the tubes of the external exchanger, being'upward, and means for discharging uncondensed vapor from the top of the exchanger, together with means for utilizing the liquid. produced in the exchanger as a reflux liquid in the fl main tray section and for purifying the said uncondensed vapor- 12. In a system for separating mixed gases, a rectifying column having a preliminary tray section, a main tray section and a vaporizer intermediate the same, external heat exchangermechanism for completing the vaporization of the liquid from the main tray section and substantially completing the liquefaction of the vapors from the preliminary tray section, and means for delivering the liquid in the external excharmer to the main tray section for use as a reflux liquid.

,13. In a system for separating air by liquefaction and rectification, the combination of interchangers, a liquefler, a rectifying column chang'ers.

WIILIAM L. DE BAUFRE. 

